[Johnson] G5RV info request
Joel R. Hallas
[email protected]
Sun, 04 Jan 2004 09:07:11 -0500
Brian,
I did not say, or mean to imply that the reflected power was lost! What I said was
that the reflected power AS SEEN AT THE TRANSMITTER is less than the reflected
power leaving the junction of transmission line and antenna due to the loss in the
transmission line. So the fact that you "measure" 2:1 at the transmitter does not
mean that you actually have a 2:1 SWR on the line, it will be higher depending on
the line loss. The crummier the line and the longer the line the better it will
look at the bottom, and the less power that will get to the antenna.
Even though your "Carolina Windom" is nominally horizontal, the first 22 feet of
feedline acts as a vertical radiator. This will provide low-angle
omnidirectional coverage with part of your power only if it is above a good ground.
Otherwise the low angle portion is dissipated rapidly.
73, Joel, W1ZR
Brian Hunsaker wrote:
> At 1:22 PM -0500 1/3/04, Joel R. Hallas wrote:
> >Gents,
> >
> >I am a happy G5RV user, but think I should point out something about both the
> >G5RV and the various Windom antennas. These antennas happen to have various
> >frequencies at which they have a somewhat reasonable match to 50 ohm coax,
> >however, at most frequencies they have a rather high swr, perhaps 5:1 to 10:1.
> >This will look lower at the transmitter end of the line due to the loss of the
> >reflected signal getting to the bridge.
> >
> >Take a look at Fig 14 of Chap 24 in the current ARRL antenna book and see the
> >additional loss in coax as a function of swr. For example foam RG-58
> >has a loss
> >of about 1.5 dB/100 ft when matched. An SWR of 5:1 will add another 1.5 dB so
> >half the power will not get to the end of the coax. It gets
> >progressively worse
> >when the SWR gets higher.
> >
> >After measuring the SWR from my G5RV, I replaced my small coax with 9913 which
> >improves the situation but doesn't eliminate it.
> >
> >The Windom seems to work best in those areas with good ground
> >conductivity where
> >the vertically polorized radiation from the feed can help. For those
> >of us with
> >rocks under the antenna, Horizontal is still best for any height.
> >
> >Just my $.02
> >
> >Joel Hallas, W1ZR
> >
> >Brian Hunsaker wrote:
> >
> >> At 7:49 PM -0700 1/2/04, KENNETH A CRIPS wrote:
> >> >Before you purchase the AES G5RV take a look a the link below this outfit
> >> >makes the best
> >> >wire antennas I know of. Their G5RV is the best "store bought"
> >>G5RV in know
> >> >of.
> >> >However the Carolina Windom they make is hands down a better antenna
> >> >
> >> >http://www.radioworks.com/PDFantenna.html
> >> >
> >> > Ken
> >> >
> >> >
> >> >
> >> >
> >> >Kenneth A. Crips Station W7ITC Cheyenne, Wyoming.
> >> >
> >> >_______________________________________________
> >> >Johnson mailing list
> >> >[email protected]
> >> >http://mailman.qth.net/mailman/listinfo/johnson
> >>
> >> I just purchased a Windom (80 - 10 version, 132') from Antennas and
> >> More - (www.antennasmore.com), and it is a real killer. I am getting
> >> great reports on 80, 40, 20, and they are all without a tuner. In
> >> fact, it loads up on 20 better with out a tuner, than if you put a
> >> tuner in the line. Mine is about 35' above the ground. Price - $122
> >> with shipping. They have G5RVs also, but I agree with Ken that the
> >> Windom is a better aerial.
> >>
> >> My two cents,
> >>
> >> Brian - W5YE
> >> --
> >> r. b. hunsaker
> >> *** The Ark was built by an amateur - the Titanic by professionals. ***
> >>
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>
> My Windom is all horizontal, so ground conductivity does not come
> into play. My swr is less than 2:1 on all bands, except 15 (which the
> manufacturer advises you in his literature).
>
> Also, regarding the subject of "loss from high swr", check out Kurt
> N. Sturba's (pseudonym) excellent work on antennas and the "myths"
> related thereto. "Aerials I, II, or III" is a must for anyone who is
> serious about learning what is and what is not, in their
> construction, and performance. Reflected power is not actually
> "lost", as most folks think.
>
> 73,
>
> Brian
> --
> r. b. hunsaker
> *** The Ark was built by an amateur - the Titanic by professionals. ***